Heat the olive oil in a large saucepan or Dutch oven over medium heat.
Add the tomato paste and cook, stirring constantly, for about 1 minute until it darkens slightly. This step is key for a rich flavor!
Add the sliced onion and diced carrot to the pot.
Season with a generous pinch of salt and pepper and cook, stirring occasionally, for about 5 minutes, or until the vegetables begin to soften.
Stir in the chopped tomatoes and thyme.
Continue to cook, stirring every few minutes, for 10-15 minutes. The tomatoes should break down and the mixture will thicken.
Pour in 2 cups (480 ml) of the warm vegetable stock and stir everything together.
Bring the soup to a simmer.
Taste the soup and adjust the seasoning. If it tastes a little too acidic, stir in the optional sugar. If the soup is thicker than you'd like, add more stock until it reaches your desired consistency.
Serve hot, garnished with fresh parsley or basil.